[Web] Return json array when mailq empty, fixes #3738

data/web/inc/functions.mailq.inc.php

@@ -71,7 +71,7 @@ function mailq($_action, $_data = null) {
       }
     }
     if (!isset($line) || empty($line)) {
-      return '{}';
+      return '[]';
     }
     else {
       return json_encode($line);

data/web/json_api.php

@@ -370,7 +370,7 @@ if (isset($_SESSION['mailcow_cc_role']) || isset($_SESSION['pending_mailcow_cc_u
                     echo $mailq;
                   }
                   else {
-                    echo '{}';
+                    echo '[]';
                   }
                 break;
               }